Optokinetic nystagmus is a visually guided pattern of reflex eye movements which serves to stabilize overall image movement. In this respect, optokinetic nystagmus differs from following eye movements which serve to maintain the image of a small object stationary on a particular retinal region (usually the area centralis). Present evidence on rabbits indicates that the visually controlled slow phase of optokinetic nystagmus is driven by the so-called direction-selective ganglion cells of the retina. These cells respond preferentially to stimulus movement in a particular direction and can therefore provide information to the central nervous system regarding both the presence and the direction of retinal image motion. There is reason to believe that the direction-selective cells send their signals to the oculomotor nuclei by a fairly direct route, probably via the superior colliculus. It is now necessary to experimentally determine the neural pathway by which retinal information reaches the oculomotor nuclei, and to study the transformations in the information which occur along this pathway. The objectives of the proposed project are 1) to determine the neural pathway involved in the slow phase of optokinetic nystagmus 2) to study the characteristics of single neurons which provide the link between retina and motor nuclei, and 3) to explain the neural mechanism for the control of optokinetic nystagmus. The techniques are those of single-cell neurophysiology in which the responses of individual neurons may be recorded with extracellular microelectrodes. The project will be concernec with the responses of individual neurons to visual stimuli, of many varieties, but particularly to those stimuli normally used to elicit optokinetic nystagmus. The experiments will be performed on rabbits since these animals exhibit optokinetic nystagmus which is uncontaminated by other reflex eye movements.